They are generic parts, not specific to Mercedes but available also at Mercedes:
N 900262 009100 binder
N 900263 009000 strap, 2x285mm needed, ordered by meter
9mm width if I remember correctly (probably can be decoded from the DIN number). I think you can buy it in a lot of automotive stores.
I am enclosing a little sketch from 190SL knowledge bank. Not exactly the same perhaps, but showing the idea.
I would buy a couple of more if you are not fluent in installing them. Based on my experience... I was sure i would start binding in the wrong direction and I did.